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Cometary Aurorae Discovered

21 Sep 2020, 18:46 UTC
Cometary Aurorae Discovered
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A long time ago, I studied comets during my years in graduate school. We studied cometary plasma tails, and found a lot of interesting things. But, we didn’t know at the time that a comet can have an aurora. That all changed with the in-depth study of Comet 67P/Churyumov-Gerasimenko. The Rosetta mission studied that comet in great detail, including emissions from and around the nucleus. Among those emissions: far-ultraviolet light that is generated when electrically charged particles from the Sun interact with the gassy coma surrounding a cometary nucleus.

From Dayglow to Cometary Aurorae

Initially, scientists interpreted the far-UV emissions as part of the “dayglow” surrounding the comet. When they re-analyzed the data, they found the emissions. The solar wind remains the culprit, just as it plays a role in forming the plasma tail of a comet. Charged particles in the solar wind interact with the gases in the coma. That actually causes water and other molecules to break apart and the resulting atoms give off far-ultraviolet light. And, that’s what forms the aurora around the comet.

Implications of Cometary Aurorae

Of course, the formation of such emissions at a comet tells scientists something about the solar wind, its ...

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